Consumers in the U.K. are being encouraged to grow fresh produce on their kitchen windowsill with the launch of a new “living lettuce,” reports The Guardian.U.K. supermarket chain Sainsbury’s sells the lettuces, which took two years of research to perfect, at selected stores. The idea behind the new lettuce â a cross of endive, gem and curly-leafed strains of the salad plant â is that consumers can harvest the plant gradually over several weeks, a few leaves at a time, so that they can have freshly-picked lettuce leaves.